An organic oil contains lipid constituents and various other concomitants, with the latter lowering the quality of products of value that are obtained from the oil, and possibly limiting the use thereof.
In accordance with the prior art, with the aim of technical refining, oils are subjected usually to a process known as degumming, in order to transfer hydratable compounds into a water phase, thus allowing the dissolved or aggregated compounds to be removed by methods for phase separation. By means of these methods, the major fraction of hydratable phospholipids, and a fraction of non-hydratable phospholipids, are removed.
This is followed by removal of remaining phospholipids and of free fatty acids as concomitants from the oil fraction. This removal may involve subjecting the free fatty acids to hydrolysis, for example. In the vegetable oil there may typically be magnesium salts and/or calcium salts and/or chelates such as chlorophyll, for example, in solution in the vegetable oil. These compounds, however, are difficult to separate from the free fatty acids, and therefore, following the removal of the free fatty acids, dissolved or undissolved alkaline earth metal salts may be present as concomitants in the free fatty acids fraction.
It is therefore an object of the present invention to provide a method for the stepwise processing of an organic oil in order to attain a low fraction of dissolved and/or undissolved alkaline earth metal compounds and/or phospholipids and/or sterylglycosides.
This object is achieved in accordance with the embodiments of the invention.
A method according to the invention relates to the stepwise processing of an oil. This stepwise processing may preferably be integrated into an established refining operation for producing an edible oil or a fuel for internal-combustion engines, as a step sequence.
The stepwise processing comprises the following steps:
A Providing a Raw Oil
The raw oil may be obtained, for example, through from plants by pressing or extraction methods. However, diverse alternative provision variants are contemplated. The raw oil here need not necessarily have been obtained directly from living entities, but may also, as in the case of frying oil, have already been used for its intended purpose one or more times.
B Degumming the Raw Oil by Adding Water and/or Acid to the Raw Oil and Forming at Least Two Phases, an Aqueous Phase and an Oil Phase, and Separating the Phospholipid-Enriched Aqueous Phase from the Oil Phase
Degumming per se is a conventional method step. A distinction is made between aqueous degumming and the more rarely employed acid degumming. The latter is preferred in the case of the methods of the invention. In one preferred variant embodiment, the addition of acid may comprise the addition of a dilute acid or, likewise preferably, the addition of a concentrated acid in conjunction with a subsequent addition of water. In this operation, primarily hydratable gums, such as hydratable phosphoglycerides, for example, such as phophatidylinositols and phosphatidylcholines, are separated from the oil phase and transferred into the aqueous phase. They can be removed centrifugally.
C Adding Sodium Hydrogencarbonate or Sodium Acetate to the Oil Phase, and Removing Alkaline Earth Metal Compounds and/or Phospholipids and/or Sterylglycerides, in Solution in an Aqueous Phase, from the Oil Phase
The addition of sodium hydrogencarbonate results in removal of alkaline earth metal compounds and/or iron compounds, thus including chlorophyll, other magnesium complexes or else calcium complexes or iron complexes, for example. The removal of iron ions or iron compounds in particular makes the oil phase less susceptible to oxidation. In some cases the alkaline earth metal compounds may take the form of phospholipids. It is particularly noteworthy that as a result of the addition of sodium hydrogencarbonate, there is also removal of non-hydratable phospholipids, preferably non-hydratable phosphoglycerides, such as phosphatidylethanolamines, for example, and even of phosphatidic acid and salts thereof, especially the alkali metal and alkaline earth metal salts thereof. This is surprising since phosphatidic acid and salts of phosphatidic acid, which are usually present in the solution in an oil fraction, are very difficult to remove from the oil phase. The fact that this can now be accomplished in such a way that the free fatty acids remain predominantly in the oil phase and can be removed as a separate fraction. Removal may be accomplished preferably by phase separation of an aqueous phase and an oil phase in a centrifugal field.
The addition of sodium acetate results in removal of sterylglycosides. This class of substance can be detected by means of thin-layer chromatography (TLC). It has emerged here that the sterylglycoside-enriched aqueous phase contains only very small fractions of other organic constituents, such as phospholipids or free fatty acids, for example.
The product after step C is an organic oil which, relative to the degummed oil fraction in step B, has a lower fraction of one or more oil concomitants (sterylglycosides, alkaline earth metal compounds and/or phospholipids) which can usually be obtained only in a form poorly separated from the free fatty acids from an organic oil. The amount of free fatty acid relative to the oil fraction from step B is surprisingly almost unchanged after step C.
Further advantageous embodiments of the invention are apparent from the dependent claims, the description, the figures, and the examples.
The free fatty acids can advantageously now be obtained by hydrolysis in a form separated from the sterylglycosides and also, as and when required, separated from the phospholipids and/or other alkaline earth metal compounds. This hydrolysis takes place in a further optional step
D Adding an Alkaline Agent to the Oil Fraction in Step C and with Removal of the Hydrolyzed Fatty Acids from the Aforesaid Oil Phase.
The removal may take place preferably as already occurred in step C, by phase separation of an aqueous phase and an oil phase in a centrifugal field.
In a further step, there may be further refining of the oil phase in step C or D as well. This is accomplished by the optional step of
E Bleaching and/or Deodorizing the Oil Phase.
Since beforehand in step C even difficult-to-remove phospholipids have been removed to a large extent from the oil phase, and since optionally even free fatty acids have been removed from the phospholipid phase, the bleaching operation can be significantly more effective. Bleaching can be accomplished particularly effectively by means of bleaching earth, for example.
Deodorizing may likewise be configured effectively. As is known, deodorizing may be accomplished mechanically by means, for example, of steam distillation in a so-called deodorizer.
Elucidated in more detail below are further advantageous embodiments of individual method steps:
It is advantageous for degumming to take place by addition of an acid selected from one or more of the following acids: citric acid, acetic acid, formic acid, oxalic acid, hydrochloric acid, sulfuric acid, nitric acid and/or phosphoric acid. Among the aforementioned acids, particular suitability for the removal of gums has been shown by the organic acids.
Particularly for the class of the phosphoglycerides, as a subclass of the phospholipids, one of the views expressed in the case of triglycerides is that, starting from the (R′CH2)—(R″CH)—(R′″CH2) scaffold structure, the respective long-chain substitutes R′, R″, and R″′ converge at elevated temperatures, meaning that hydration and hence the transition to a water phase and the removal of these substances are made more difficult. At the same time, however, there is also an increase in the viscosity of the oils in question.
It has emerged that the degumming of an oil according to step B and also the addition of sodium acetate and/or sodium hydrogencarbonate according to step C are possible at a temperature of more than 65° C. in spite of the aforesaid difficulties, with the degumming at a temperature in the range of 66-95° C. constituting a particularly good compromise between the two aforementioned effects.
Customarily, moreover, the expectation with the addition of sodium hydrogencarbonate in the form of an aqueous solution is that it would lead to more effective separation of the concomitants present in the oil phase, since the solution already contains hydrated cations and anions. It has emerged, however, that even the addition of sodium hydrogencarbonate and/or sodium acetate in the form of powder or in the form of suspension to the oil phase in step C added, and optionally a subsequent addition of one, compared to a solution, leads to a comparably good and selective outcome in the deposition of concomitants from the oil phase. At the same time, however, substantially less of a water phase requiring work-up is produced. The addition of water takes place advantageously before or after the addition of the powder.
Particularly good outcomes have been achieved on addition of more than 0.1 wt % of sodium hydrogencarbonate and/or sodium acetate, based on the total weight of the oil phase in step C.
It has emerged, moreover, that on addition of at least 1.0 wt % of water, based on the total weight of the oil phase in step C, very good removal of concomitants is achieved.
The addition of sodium hydrogencarbonate according to step C may be repeated until the haze of the water phase and/or an alkaline earth metal ion content found in the oil phase and/or a phosphorus content found in the oil phase falls below a specified setpoint value. A specific result of making the addition in the form of a powder or suspension, and adding comparatively little water, is that no extensive water phase requiring work-up is produced. As a result, step C can be carried out repeatedly without the processing becoming uneconomic because of solvents obtained. At the same time, the multiple addition achieves quantitatively improved removal of concomitants.
Following the addition of sodium hydrogencarbonate in step C, it is possible with preference to remove an aqueous phase containing a free fatty acid fraction corresponding to removal of less than 1% age point of free fatty acids from the oil phase. The reporting of percentage points is based on the decrease in the total amount of free fatty acids in the oil phase. It has emerged that on addition of sodium hydrogen, irrespective of the total amount of free fatty acids in the oil, it is possible to transfer consistently less than 1 percentage point into the water phase, whereas, for example, phospholipids, chlorophyll or other alkaline earth metal compounds are transferred in large portions into the aqueous phase.
In one preferred version, after the addition of sodium hydrogencarbonate in step C, an aqueous phase can be removed which comprises a fraction of free fatty acids corresponding to removal of less than 0.2% age points of free fatty acids from the oil phase.
This comparatively high degree of purity is achievable, but can also be smaller through reduced metering, according to the interest of the user.
Through the addition of sodium acetate in step C, it is possible with preference to achieve removal of an aqueous phase in which organic constituents are present, in solution or suspension, which contain more than 30 wt %, preferably more than 50 wt %, of sterylglycosides.
Following step C, it is possible with preference, in a step D, to perform hydrolysis of free fatty acids with addition of an alkaline agent to the oil phase from step C, thereby making it possible for these hydrolyzed fatty acids to be removed from the oil phase. The hydrolyzed fatty acids here may be transferred, as a relatively pure fraction from the oil phase, into an aqueous phase, which is formed by addition of water before, during or after the addition of the alkaline agent.
The hydrolyzed fatty acid may have preferably less than 3 wt %, preferably less than 1 wt %, of organic impurities. These soaps may be subsequently cleaved back to free fatty acids under pressure or with addition of acid. This reaction is commonly known as soap cleaving. In view of the relatively high purity of the soap fraction, the water phase obtained in the soap cleaving is not very contaminated. Contaminated soap fractions, on the other hand, would make soap cleaving more difficult.
Following step C or D, the oil phase from step C or D can be bleached and/or deodorized. This removes unwanted colorants and removes unwanted odorants and flavors from the oil phase. These are usually concluding steps in the refining of an oil for production of edible oils or fuels.
The added alkaline agent in step D may preferably be an inorganic alkali metal hydroxide solution, preferably a sodium hydroxide solution. The addition of this comparatively inexpensive agent is sufficient, following removal of sterylglycosides and/or phospholipids and/or alkaline earth metal compounds, to give an oil phase which is predominantly free from concomitants.
Provided in accordance with the invention, furthermore, is an apparatus configured to perform a method according to the invention.